Lithium base lubricating grease method

ABSTRACT

A METHOD IS DISCLOSED FOR THE LOW TEMPERATURE PREPARATION OF A LITHIUM BASE LUBRICATING GREASE HAVING THE DESIRED PORPERTIES WHEREIN THE NEED FOR EITHER SHEARING OR MILLING IS ELIMINATED. FURTHERMORE, THE RESULTING GREASE HAS EXCELLENT MECHANICAL STABILITY. THIS METHOD COMPRISES RAISING THE TOP TEMPERATURE OF THE SAPONIFIED MIXTURE TO WITHIN A SPECIFIED NARROW TEMPERATURE RANGE. THE LATTER IS RELATED TO THE ANILINE POINT OF THE LUBRICATING OIL IN THE COMPOSITION WHOSE TOP TEMPERATURE FALLS WITHIN THE AFOREMENTIONED TEMPERATURE RANGE.

Feb. 5, 1914 H HOMM R 3,790,479

LITHIUM BASE LUBRICATING GREASF METHOD Filed Dec. 21. 1970 2 Sheets-Sheet 1 FIGURE 1 TIME :lo HHFLLVHEIdWlL INVENTOR GORDON H. HOMMER BYMQMWQF,

ATTORNEY "United States Patent O 3,790,479 LITHIUM BASE LUBRICATING GREASE METHOD Gordon H. Hommer, Wallingford, Pa., assignor to Sun Oil Company of Pennsylvania, Philadelphia, Pa. Filed Dec. 21, 1970, Ser. No. 100,249 Int. Cl. C10m /14 U.S. Cl. 252-41 1 Claim ABSTRACT OF THE DISCLOSURE A method is disclosed for the low temperature preparation of a lithium base lubricating grease having the desired properties wherein the need for either shearing or milling is eliminated. Furthermore, the resulting grease has excellent mechanical stability. This method comprises raising the top temperature of the saponified mixture to within a specified narrow temperature range. The latter is related to the aniline point of the lubricating oil in the composition whose top temperature falls within the aforementioned temperature range.

CROSS REFERENCES TO RELATED APPLICATIONS The present application is copending with the following applications, filed of same date herewith: Calcium Base Lubricating Grease Method, Ser. No. 99,905, and Sodium Base Lubricating Grease Methods, Ser. No. 99,906, both noW abandoned. These applications have the same inventorship and common ownership.

BACKGROUND OF THE INVENTION This invention relates to the preparation of a lubricating grease, the latter being a solid to semi-fluid product of a dispersion of a thickening agent in a liquid lubricant. Other ingredients imparting special properties can be included. More specifically, this invention relates to an improved low temperature method for preparing a lithium base lubricating grease.

The low temperature procedure for preparing a lithium base grease generally involves saponifying a sponifiable fatty material, e.g., commercial 12-hydroxystearic acid, with a saponifying agent, e.g., lithium hydroxide. This saponification normally takes place in at least a portion of the lubricating oil, e.g., petroleum lubricating oil, contained in the grease at a temperature lower than the freezing point of the resulting soap-oil mixture. The soap is the lithium-fatty material resulting from the saponification reaction. Thereafter the soap-oil mixture is heated to an elevated temperature which is below the melting point of the soap-oil mixture; during this heating, low boiling saponification by-products and added water evaporate. After being heated to this elevated temperature, the soapoil mixture is allowed to cool. Furthermore, during the aforementioned heating and cooling, any additional lubricating oil or cut back oil required to provide a grease of desired grade is added to the saponified mixture. In some methods, the grease is milled during or after cooling; in other methods, the grease is sheared before cooling. Milling of the grease can be performed by a colloid mill, for example while shearing suitably can be performed by means of a valve properly located in the system and having suflicient pressure drop to obtain the proper consistency of the grease.

The present invention provides a low temperature procedure wherein neither shearing nor milling is required to obtain the desired grease properties. In addition, the resulting grease, despite the lack of shearing or milling, has excellent mechanical stability.

3,790,479 Patented Feb. 5, 1974 SUMMARY OF THE INVENTION A lithium soap thickened grease having the desired properties and, in addition, excellent mechanical stability, is prepared without shearing and/or milling by the improvement defined hereinafter to the low temperature method of preparing said grease. In the low temperature method, after the saponification mixture of lithium base saponifying agent and a saponifiable hydroxy fatty material is saponified in the presence of at least part of the lubricating oil contained in the finished grease and undesirable low boiling materials have evaporated, the mixture is further heated to an elevated temperature to obtain the desired grease properties; afterwards it is allowed to cool. During the aforementioned heating and cooling, the balance of any lubricating oil or cut back oil required to provide a grease of the desired grade is added to the mixture. The present improvement involves heating the mixture, during said heating step, to a maximum temperature within a specific narrow temperature range, herein referred to as the top temperature. This range is related to the aniline point of the lubricating oil in the composition being heated to the top temperature, and the relationship is defined in FIG. 11 which is explained under the Description section herein.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a graphic presentation of a typical temperature versus time relationship or temperature profile encountered when preparing a batch of lithium soap thickened grease in accordance with this invention. This temperature profile shows how the top temperature range used in this invention relates generally to the preparation of a lithium base grease. This figure is also used to assist in defining shearing and milling. FIG. II relates the necessary top temperature range, referred to generally in FIG. 1, to the aniline point of the lubricating oil present in the composition being heated to within the top temperature range.

DESCRIPTION The general method of preparing a lithium soap grease according to this invention can be described using the temperature-time profile shown in FIG. I. Solid lithium hydroxide, for example, is added at time-temperature 1 to a suitable container, e.g., a heatable kettle containing a stirring device, and then Water is added 1a; normally, both would be at ambient temperature. For convenience hereinafter, a time-temperature point or line in FIG. I is referred to by just a number or a letter. The solution is heated and agitated to insure that the lithium hydroxide dissolves. After the hydroxide dissolves, at least a portion of the lubricating oil to be ultimately incorporated into the grease is added to the kettle containing the aqueous solution 2. If the temperature of the oil is lower than the temperature of the aqueous solution, the temperature of the mixture in the kettle can be held constant by adding the oil at a rate such that, coupled with the heat input to the kettle, the temperature will remain constant 3. After the constant temperature period 3, heating again increases the temperature 17. On the other hand, if the oil is at a higher temperature or sufficient heat is added to compensate for a lower temperature oil, then the temperature of the mixture continues to increase 4. After the addition of the lubricating oil, the saponifiable hydroxy fatty material, e.g., commercial 12-hydroxystearic acid, is added 7. During the addition of this acid, the temperature of the resulting mixture can be held constant 5 and increased afterword 18, or it can be continuously increased 6. Saponification occurs during time span 8. After saponi fication, the temperature of the saponified mixture can be increased to drive off low boiling saponification by-products 19 and added water. Alternatively the temperature can be increased to some temperature 20 and maintained at that temperature until said low boiling materials are evaporated and after which the temperature is increased 21. In either alternative 19 or 20-21, heating is continued until the temperature necessary to obtain the desired grease properties is reached 11.

This necessary temperature is the maximum temperature or the highest elevated temperature that the soap-oil composition experiences and which falls within the top temperature range 11. This top temperature range 11 is a narrow range which lies between the melting point and the freezing point 12 of the soap-lubricating oil composition. As shown in FIG. 11 and explained hereinafter, this top temperature range is related to the aniline point of the lubricating oil contained in the soap-lubricating oil composition.

After the temperature of the soap-lubricating oil composition reaches the top temperature range 11, the composition can be cooled 13. Alternatively, the composition can be cooled to a certain temperature and maintained at that temperature for a period and then the cooling continued 14. Also, the mixture can be partially cooled after reaching the top temperature range 11, but then reheated to a higher temperature, which is not above the freezing point 12, followed by further cooling 15.

The length of time 16 the soap-lubricating oil composition stays Within the top temperature range is not critical. Thus, heating of the kettle can stop as soon as the desired temperature is reached throughout the entire mixture and the length of time at the top temperature can be determined by the natural cooling of the equipment and materials in the kettle. Alternatively, the composition can be maintained at the desired temperature for an extended period.

The balance of any lubricating oil, also referred to as cut back oil, required to provide a grease of the desired grade can be incorporated into the soap-oil composition after saponification, i.e., during the evaporation of the lower boiling materials, or during the heating to the desired top temperature, or during cooling. Preferably, the cut back oil is added after the evaporation since any oil added during this period can interfere with the evaporation of low boiling saponification by-products and added Water. This cut back oil, or oils, can have the same composition as the portion of the oil initially added to the aqueous solution or it can have some other composition or compositions. Also, this cut back oil is carefully added to and carefully stirred into the soap-oil composition after saponification.

By carefully controlling the maximum temperature of the soap-lubricating oil composition to within a narrow top temperature range 11, the resulting grease does not require shearing or milling at any time during its manufacture to obtain the desired grease properties. The elimination of shearing or milling reduces the time required to make a grease and reduces operating costs. Shearing refers to subjecting the soap-lubricating oil composition or the mixture of said composition and any or all of the portion of the balance of any required oil to a strong force which slips or slides one part of the mixture relative to an adjacent part, prior to cooling, to obtain a finished lithium base lubricating grease which will afterwards change little in consistency while in use. The invention described in US. Pat. 3,244,628, issued Apr. 5, 1966 to William R. Hencke et al., uses a partly closed valve with a pressure drop of about 10 to 200 pounds per square inch across the valve to obtain said shearing.

When a grease would be subjected to this shearing in published methods can be visualized by reference to FIG. I. Heretofore, shearing would occur at any time to the left of the dashed line Z or at any temperature above the dashed line Y, both lines being shown in FIG. I. In other words, shearing would occur on any portion of the temperature-time profile line after saponiftcation except in 4 the area to the right of the dashed line Z and below the dashed line Y.

Milling refers to subjecting the cooled mixture of soaplubricating oil composition and the balance of any required lubricating oil to a force to obtain a finished lithium base lubricating grease which will afterwards change little in consistency while in use. US. Pat. 3,242,082, issued Mar. 22, 1966 to Lloyd F. Badgett et al., mentions an apparatus that can be used for this purpose. In the temperature-time profile of FIG. 1, milling heretofore would occur any time and at any temperature within the area enclosed by dashed lines Z and Y.

Consistency refers to the flow characteristic of the grease under pressure. The cone penetration test (ASTM Method D2l7-52T) is a measurement of this characteristic.

The aforementioned shearing and milling refers to the intentional application of substantial shear to the dispersion of thickening agent in the lubricating oil to obtain a finished product. However, in the manufacture of lithium base lubricating grease by the present invention, the dispersion may be subjected to the unintentional application of an insignificant amount of shear by mixing during saponification, heating, cooling and furthermore, during the transfer of the grease; e.g., pumping of the grease from the kettle to the product containers. Thus, the dispersion prepared according to this invention can be subjected to low intensity shear for a very limited duration without modifying the grease structure or adversely altering the mechanical stability.

In the method of the present invention, the lithium hydroxide is dissolved in hot water and then at least a portion of the lubricating oil to be ultimately used is added to the hot solution. However, a satisfactory alternative method is first to place said portion of oil in the empty kettle and subsequently add hot lithium hydroxide solution previously prepared in another container.

FIG. II specifically defines the top temperature range shown generally in FIG. I. FIG. II is a graph relating the aniline point of the lubricating oil component of the soaplubricating oil composition at the time the compositions temperature is within the top temperature range necessary to practice this invention. The area enclosed by ABCD represents the operable top temperature range; the area enclosed by EFCD represents a more preferable top temperature range; the area enclosed by EFGH represents the most preferable top temperature range. Thus, for example, with an oil or blend of oils having an aniline point of 220 F., the operable top temperature range is 371 F. to 395 F.; a preferred top temperature range is 371 F. to 391 F.; the most preferable top temperature range is 382 F. to 391 F. Also shown in FIG. II are the equations for the lines shown thereon.

These equations are as follows:

Temperature, F. =0.140 (aniline point, F.) +364 Temperature, F.=0.116 (aniline point, F.) +365.8 Temperature, F. =0.0944 (aniline point, F.) +3611 Temperature, F. =0.0876 (aniline point, F.) +3513 wherein the aniline point is 360 F.

Surprisingly, the omission of shearing or milling when using the top temperature range of present invention does not adversely change the mechanical stability. Even more surprisingly, the contrary occurs; i.e., the mechanical stability of the lithium base lubricating grease prepared by this invention is better than a grease prepared with shearing or milling. Mechanical stability is defined herein as the numerical difference in penetration of the lithium base lubricating grease after rolling, i.e., Standard Method of Test For Roll Stability of Lubricating Grease, ASTM D1831-64, and after 60 strokes, i.e., Standard Method of Test For Cone Penetration of Lubricating Grease, ASTM D217-68. The smaller this numerical difference, everything else being equal, the more desirable the grease.

While this invention can be carried on in a batch, semicontinuous or continuous system, it is preferable that the system be a batch one.

The term lithium base saponifying agent as used herein refers to lithium compounds which saponify fatty materials. Included within this definition are lithium hydroxide, lithium oxide and lithium carbonate. Preferably lithium hydroxide is used in the method defined herein. The saponifying agent is generally added in aqueous mediums.

Oils which can be employed for forming the soap-oil composition and the lithium base lubricating grease include the oils normally referred to as lubricating oils. Suitable lubricating oils, synthetic or mineral, are those having Saybolat Universal viscosities of about 40-6000 seconds at 100 F. Suitable petroleum lubricating oils can be naphthenic, paraflinic, aromatic, or asphaltic in type or blends of any of these. Preferably the oil is either naphthenic or parafiinic. The aniline point of the petroleum lubricating oil, as determined by Standard Test for Aniline Point and Mixed Aniline Point of Petroleum Products and Hydrocarbon Solvents, ASTM D611-64, is about 120 F.-360 F. Furthermore, an oil which is substantially unreactive under the saponification conditions is preferably employed in the forming of the grease, petroleum lubricating oils being particularly suitable for this purpose.

Suitable saponifiable fatty materials which can be employed in the production of a lithium base lubricating grease include hydrogenated castor oil, hydrogenated triglycerides of ricinoleic acid, hydrogenated ricinoleic acid, hydroxystearic acids and, in particular 12-hydroxystearic acid, methyl or ethyl esters of hydroxystearic acid and, in particular, the methyl or ethyl ester of l2-hydroxystearic acid. It is preferred that the saponifiable fatty material contains at least 50 weight percent hydroxystearic acid and more preferably at least 75 weight percent 12-hydroxystearic acid.

Commercial grades of l2-hydroxystearic acid can contain minor amounts of other saturated fatty acids such as arachidic and n-nonadecylic and unsaturated fatty acids such as palmitoleic, petroselinic, petroselaidic, elaidic, vaccenic and gadoleic. The fatty material resulting from a hydrogenated castor oil from which glycerol has been removed also contains minor amounts of other fatty acids. For example, one commercial grade of such a material contains by weight: 86.5% of 12-hydroxystearic acid, 1% oleic acid, 2.5% ricinoleic acid, 2% palmitic acid and 8% stearic acid.

As mentioned heretofore, the saponifiable fatty materials include the methyl and ethyl esters of hydroxystearic acid and, in particular, the methyl ester of 12-hydroxystearic acid. When one of these esters is used, the rate of reaction between it and the lithium base saponifying agent, e.g., lithium hydroxide, is slower than the rate of reaction between, e.g., just l2-hydroxystearic acid and lithium hydroxide. Thus, the manufacturing time is greater when using esters than when using hydroxystearic acid. Furthermore, the alcohol coproduct, e.g., methanol, formed during the saponification of the methyl ester is evaporated during the process and unless recovered, is lost.

The percentage of lithium soap in the finished grease product depends on the end use requirement. Thus, for example, some textile greases have a soap content as low as 0.25%, while some heavy industrial greases have a soap content as high as 30%.

The greases produced in accordance with this invention can contain various additives of the usual type such as corrosion inhibitors, oxidation inhibitors, extreme pressure agents and anti-wear agents. These additives can be added either before or during the cooling process. The additions are preferably performed while the temperature of the grease is between 300 F. and about F., suitably during the cooling step.

The desired properties or desired grade of grease refers to the physical arrangement of the component particles of a lubricating grease thickener, additive-if anyand the lubricating oil. It is the nature and stability of this arrangementwhich determines the appearance, texture and chemical and physical properties of the grease. Appearance refers to those characteristics of a grease which are observable by visual inspection only, e.g., bulk appearance, bloom, color and luster. Bulk appearance refers to visual appearance of the grease where the undisturbed surface is viewed in an opaque container. Bloom is the surface color, usually blue or green, of the grease when viewed by reflected daylight at an angle of about 45 from the surface. Color of a grease is the shade and the intensity shown when the grease is viewed under conditions to eliminate bloom. The intensity of light reflected by a grease, its sheen or brilliance refers to the luster of the grease. Texture is that property of the grease which is observed when a small separate portion of it is pressed together and then slowly drawn apart.

Physical and chemical properties, which relate to the grease grade, are defined-along with the test procedures necessary to measure these properties-in 1970 Book of ASTM Standards, Part 17, Library of Congress Catalog Card Number 40*10712. In addition, other properties and test procedures are defined and used by government agencies, e.g., the Department of Defense, and private laboratories and are reported in various trade journals, e.g., NLGI Spokesman (National Lubricating Grease Institute). Some of these tests are reported in various texts, e.g., Manufacture and Application of Lubricating Greases, C. J. Boner, Library of Congress Catalog Card Number 54-11031.

The following examples illustrate this invention and also provide comparisons between this invention and current methods.

EXAMPLES The general procedure for making the lithium base greases shown in the accompanying tables was as follows.

46.5 grams of a typical commercial lithium hydroxide were added to a 12 lb. electrically heated laboratory kettle equipped with counter-rotating sets of paddles. Then 200 grams of water were added to the kettle and the resulting mixture heated to a temperature of 200 and maintained at said temperature until the lithium hydroxide dissolved. Thereafter, 1975 grams of a naphthenic oil were added slowly to the kettle, causing the temperature of the liquid mixture to drop. After the temperature of the liquid in the kettle returned to- 180 F., 300 grams of a typical commercial l2-hydroxy-stearic acid were added in 6 approximately equal portions. Afterwards, the amount of heat was increased and, as a result, water was driven off. During this entire procedure, the liquid was gently stirred.

After the water had been evaporated from the mixture in the kettle, the temperature of the mixture was gradually raised to a suitable top temperature. Then the heat was turned off and the mixture was allowed to cool to about 340-350 F. At this temperature, 365 grams of said naphthenic oil, i.e., a cut back oil, were slowly added to the stirred kettle. This addition was followed by the addition of 2213 grams of a different naphthenic oil, i.e., another cut back oil. During the addition of both cut back oils, suflicient heat was applied so that the temperature of the dispersion dropped to only about 300 F. The resulting grease was held at about 300 F. for 15 minutes and then allowed to cool to F. and packaged. Later, samples were taken for tests to determine grease structure.

The first naphthenic oil added in two portions (1975 grams and 365 grams) had the following properties: viscosities, SUS @100 F. of 514; SUS @210 F. of 52.4;

7 API gravity @60 F. of 19.6; pour point of F.; aniline point of 153 F. The third added naphthenic oil had the following properties: viscosities, SUS @100 F. of 5945; SUS @210 F. of 135; API gravity @60 F. of 17.3; pour point of +20 F.; aniline point of 185 F.

The accompanying Table I lists, as an example, the numerous runs performed to obtain the data necessary to locate the top temperature range (shown in FIG. 11) for a soap-lubricating oil composition whose oil had an aniline point of 153 F. Other runs were performed using oils having a wide range of aniline points to obtain the data necessary to develop the relationships shown in FIG. ll.

Also shown in Table I are the melting and freezing points of the soap-lubricating oil composition prepared with a lubricating oil having an aniline point of 153 F. The melting point of said soap-oil composition was 392.S F., i.e., several degrees higher than the top temperature used in Runs 3-14, demonstrating that this invention relates to a low temperature method. This melting point is also known as solution temperature, while the freezing point is also known as crystallization temperature. Tests for determining both melting and freezing points are described in US. Pat. 2,652,366, Robert C. Jones et a1., Sept. 15, 1953.

Runs 7, 8, 9, 10, 11, and 12 shown in Table 1 indicate that satisfactory greases were prepared, without milling or shearing, at the top temperatures shown. Surprisingly, the greases of Runs 7, 8, 9, 10 and 11 had excellent mechanical stability, i.e., the penetration differences between after rolling (ASTM 131831-64) and after 60 strokes (ASTM D217-68) were less than 62. The lower the latter value, the greater the mechanical stability.

The criticality of the top boundary of the top temperature range can be illustrated by comparison of Runs 7 and 5. The former had a top temperature of 384 F., whereas the latter had a top temperature of 385 F. Thus, only 1 difference existed, yet the grease of Run 7, without milling, was satisfactory, whereas the grease of Run 5, without milling, was not.

As the top temperature used to prepare a lithium base grease by this invention approaches the freezing point of the soap-oil composition, the structure of the resulting lubricating grease becomes poorer. Thus, for example, comparison of the grease prepared in Runs 11 and 12 shows that, as the top temperature approached the freezing point, the ASTM penetration after 60 strokes increased from 295 to 332. With a given soap concentration, the lower the penetration number, the higher the yield of grease, the latter being desirable. Comparison of Runs 12, 13 and 14 indicates that, while greases prepared at top temperatures approaching the freezing point can be satisfactory, if milled, the resulting mechanical stability is substantially poorer than when higher top temperatures are used.

While this invention relates to a low temperature method of preparing greases, several runs were made at melt temperatures for comparative purposes. Thus, Run 1 illustrates a melt temperature method of preparing, with milling, a satisfactory grease having a typical mechanical stability. Run 2, compared to Run 1, indicates the need for milling in preparing a satisfactory grease at a melt temperature.

Runs 3, 4, 5, and 6 demonstrates that a temperature range exists between the melting point of the soap-oil composition and the top temperature necessary to practice this invention wherein, without milling, the resulting grease has an unsatisfactory structure.

While the greases shown in Table I were prepared with a naphthenic oil, the greases in the accompanying Table II were prepared with a paraflinic oil. Comparison of Runs 15, 16, 17 and 18 in Table 11 indicates that within the melting and freezing points of the soap-paratfinic lubricating oil composition is a narrow top temperature ing a satisfactory structure and excellent mechancal stability can be prepared without milling or shearing. These lithium base greases were prepared in a similar manner described for the naphthenic greases reported in Table I except for the following: the lubricating oils used were parafiinic rather than naphthenic; two different paraflinic oils were used prior to the temperature of the soap-oil composition reaching the top temperature range; no cut back oil was used.

The first paraffinic oil used to prepare the greases in Table II had the following properties: viscosities, SUS F. of 508; SUS @210 F. of 64.3; API gravity @60 F. of 30; pour point of 0 F. The second oil used had these properties: SUS @100 F. of 2900; SUS @210 F. of 165; API gravity @60 F. of 27.2. The resulting aniline point of the blended oils was 248 F.

Comparison of Runs 19 and 20, 21 and 22, as reported in the accompanying Table III, demonstrates that milling the greases prepared within the top temperature range of this invention reduces the mechanical stability of the grease. Runs 19-20 were made with a naphthenic oil; Runs 21-22 were made with a parafiinic oil.

Two runs, 23 and 24, as reported in Table IV, demon strate that lubricating oils having substantially difierent aniline points can be used to prepare satisfactory lithium greases according to this invention. The mechanical stability of the grease prepared in Run 24 was -14; this does not indicate that the grease was unsatisfactory. On the contrary, the -14 value indicates that the grease became stiffer with use which can be desirable in certain applications.

In Tables I, II, III and IV, penetrations after 60 strokes and after 100,000 (100M) strokes were according to Standard Method of Test for Cone Penetration of Lubricating Greases (ASTM D217-68); roll penetration according to Standard Method of Test for R011 Stability of Lubricating Greases, (ASTM D1831-64) at 24 hours, 160 r.p.m., and F.; the milling, where indicated, was performed by a typical mill used for finishing greases.

Other lithium base lubricating greases, containing 6-20 weight percent lithium soap, were prepared using a fatty material containing 30-90 weight percent triglycerides obtained from hydrogenated castor oil with the balance being commercial 12-hydroxystearic acid. The results were analogous to those reported for the runs in which the fatty material was just the commercial 12-hydroxy stearic acid. Thus greases having the desired structure were prepared using the aforementioned triglycerides. Use of other oils, i.e., synthetic and natural, will result in satisfactory greases.

TABLE I.INFLUENCE OF TEMPERATURE, MILLING ON GREASE PROPERTIES (6% lithium soap and lubricating oil having aniline point of 153 F.)

Mechanical ASTM penetration aiterstability,

A penetra- Run Temp 1 Mil- 60 100 M tion roll, No. F.) ling strokes strokes Roll 60 strokes 1- 410 Yes 273 345 399 126 2- 410 No-.. 400 Nonhomogeneous 392. 5 No Melt pt. (solution temperatl1re) 3- 390 No-.- Grainy texture with oil separat on 4- 386 No. Grainy texture with oil separat on 1 5. 385 No-.- Grainy texture with oil separation 385 Yes-- 294 315 356 62 384 No..- 299 307 314 15 382 NO 277 294 324 47 381 N 0 269 287 313 44 380 N0 279 294 320 41 378 No 295 355 60 12 376 No 332 352 399 67 13 365 No 400 Nonhomogeneous 14- 365 Yes- 311 351 4 103 345 Freezing point (crystallization temperature) 1 Fat y material was commercial 12-hydr0xystearie acid.

TABLE II.-INFLUENCE OF TEMPERATURE, MILLING ON GREASE PROPERTIES 1 (8% lithium soap and lubricating oil having aniline point of 248 F.)

Mechanical ASTM penetration after stability,

A penetra- Run Temp. Mil- 60 100 M tion roll, No. F.) ling strokes strokes Roll 60 strokes 408 Melting pt. (solution temperature) 15- 398 Yes 342 358 375 16. 398 No 400 Nonhomogeneous 17- 390 N 294 306 308 14 18.- 384 N0. 317 323 367 50 360 Freezing point (crystallization temperature) 1 Fatty material was commercial 12-hydroxystearic acid.

TABLE Ill-INFLUENCE OF MILLING ON GREASE PROP- 1 Fatty material was commercial 12-hydroxystearic acid. 1 Oils used in runs l920 were naphthenic; in runs 22-23 parafiinic. 3 Milling was at 3,500 p.s.1.

TABLE IV.-INFLUENOE OF ANILINE POINT OF LUBRI- CATING OIL ON GREASE PROPERTIES Mechanical Ani- AS'IM penetration aiterstability,

line Top A penetra- Run point temp. 60 100 M tion roll, N 0. F.) F. strokes strokes Roll 60 strokes 1 Fatty material was commercial l2-hydroxystearic acid.

The invention claimed is: 1. In the low temperature preparation of a lithium base lubricating grease which eliminates the need for shearing or milling the grease by the process wherein a saponifiable hydroxy fatty material containing at least weight percent of 12-hydroxystearic acid is saponified with an aqueous lithium base saponifying agent selected from the class consisting of lithium hydroxide, lithium oxide and lithium carbonate, in the presence of at least a portion of the lubricating oil to be contained in the grease product, wherein the resulting saponified mixture is mixed by simple stirring only and is heated to an elevated temperature whereby low boiling saponification by-products and added water are evaporated and the oil and soap become transformed into a grease having high mechanical stability, the improvement which comprises the lubricating oil being a petroleum lubricating oil having a viscosity of 406000 SUS at F. and an aniline point of 360 F. and the top temperature reached during the heating step being within area EFGH of FIG. II, thereafter cooling the mixture and adding any additional oil needed to provide a grease of the desired grade.

References Cited UNITED STATES PATENTS 3,242,082 3/1966 Badgett et al. 252-41 3,244,628 4/1966 Hencke et a1. 252-41 3,242,084 3/1966 Bright et al. 252-41 3,242,086 3/1966 Dowden et al. 252-41 2,607,734 8/1952 Sproule et al. 25241 2,940,931 6/1960 Nelson 25241 2,947,696 8/1960 Nelson 25241 3,068,174 12/1962 Pelton et al. 252-41 3,211,650 10/1965 Oswalt 25241 3,173,869 3/1965 Watson et al. 252--39 5 PATRICK P. GARVIN, Primary Examiner I. VAUGHN, Assistant Examiner 

